Circuit breaker

ABSTRACT

THE CIRCUIT BREAKER ASSEMBLED IN A MOLDED CASING INCLUDES FOR EACH POLE THEREOF TWO CONTACTING MEMBERS HAVING CONTACTING POINTS AT THEIR TIPS, THE TWO CONTACTING MEMBERS BEING SO ARRANGED THAT AN ELECTROMAGNETIC REPULSIVE FORCE IS CREATED THEREBETWEEN WHEN A CURRENT PASSES THROUGH THE CONTACTING MEMBERS AND THE CONTACTING POINTS AT THE TIME THE CIRCUIT BREAKER IS CLOSED, AT LEAST ONE OF SAID CONTACTING MEMBERS BEING FURTHER PROVIDED WITH CURRENT LIMITING ENGAGEMENT PARTS, WHICH ARE RELEASED WHEN THE CURRENT PASSING THROUGH THE CIRCUIT BREAKER EXCEEDS A PREDETERMINED VALUE. UPON DISENGAGEMENT OF THE EMGAGEMENT PORTIONS, THE CONTACTING MEMBERS ARE ABRUPTLY SEPARATED BY THE ELECTROMAGNETIC REPULSIVE FORCE, AND THE CURRENT PASSING THROUGH THE BREAKER IS INTERRUPTED. THE ENGAGEMENT PARTS ARE REENGAGED WHEN THE CONTACTING MEMBERS ARE OPENED AT THEIR MAXIMUM OPENING POSITIONS BY MEANS OF, FOR INSTANCE, A CONVENTIONAL TRIPPING MECHANISM.

Feb. 9, 1971 nRY'QJI OZAK, ET AL 3,562,680

CIRCUIT BREAKER 3 Sheets-Sheet 1 Filed Sept. 17, 1969 N m W s O P D E sO I.. C

N m W S O D' on mm UP NO O PF1, m Dn *lf` FIG.3

INVENTOR` OZA KI ET AL Feb. 9, 19.71

Filed sept. 17, 1969 RYOJI ozAKl ETAL CIRCUIT BREAKER 5 Sheets-Sheet 2INVENTORJ` RYOM OZAKI ET AL Hrrwtfvevf Feb. 9, 1971 Filed Sept. l?, 1969RYOJI OZAKI ETAL CIRCUIT BREAKER 5 Sheets-Sheet 5 INVENTORJ RYOJI OZAK!ET AL :United States Patent O 3,562,680 CIRCUIT BREAKER Ryoji Ozaki,Kunio Igarashi, and Kiyoshi Kandatsu, Kawasaki-shi, KanagaWa-ken, Japan,assignors to Fuji Denki Seizo Kabushiki Kaisha, Kamigawa-ken, JapanFiled Sept. 17, 1969, Ser. No. 858,768 Int. Cl. H01h 77/10 U.S. Cl.335-16 8 Claims ABSTRACT OF THE DISCLOSURE The circuit breaker assembledin a molded casing includes for each pole thereof two contacting membershaving contacting points at their tips, the two contacting members beingso arranged that an electromagnetic repulsive force is createdtherebetween when a current passes through the contacting members andthe contacting points at the time the circuit breaker is closed, atleast one of said contacting members being further provided with currentlimiting engagement parts, which are released when the current passingthrough the circuit breaker exceeds a predetermined value. Upondisengagement of the engagement portions, the contacting members areabruptly separated by the electromagnetic repulsive force, and thecurrent passing through the breaker is interrupted. The engagement partsare reengaged when the contacting members are opened at their maximumopening positions by means of, for instance, a conventional trippingmechanism.

BACKGROUND OF THE INVENTION This invention relates generally toelectrical circuit breakers and more particular to a new and improvedcircuit breaker having a high interrupting capacity.

In general, various circuit breakers of the type wherein two contactshaving contact points at their tips are so arranged as to becomeparallel when closing a circuit path, and when a large current such as ashort-circuit current flows through the path, the two parallel contactsare opened apart directly by the electromagnetic repulsion forcegenerated therebetween the interrupting time being shortened and theshort-circuit current being limited thereby to increase the interruptingcapacity are known.

However, since all of these known circuit breakers have an organisationwhereby the contacts are caused directly by electromagnetic repulsion toopen apart, when a large current flows instantaneously, the contactswhich have opened apart once for an instant close again in some cases,thereby giving rise to fusion seizure for sticking of the contactpoints.

Furthermore, when an excessive current ows, the contact pressure isreduced by the electromagnetic repulsive force, whereby there is therisk of overheating of the contact parts and of fushion seizure of thecontact points.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a circuit breaker which has an organisation similar to that ofthe above described conventional circuit breakers, that is, wherein theelectromagnetic repulsive force between two parallel contacts isutilised to shorten the interrupting time and limit the short-circuitcurrent thereby to increase the interruption capacity, but in which theabove described difliculties accompanying known organisations have beeneliminated.

According to the present invention, briefly summarized, there isprovided a circuit breaker comprising a movable contacting member and astationary contacting member both arranged so that au electromagneticrepulsive force ice is created therebetween by a current passing throughthe two members, a holder connected with at least one of the twomembers, said at least one of the contacting members and said holderincluding parts engageable at a position nearer to contacting points ofthe two contacting members than the acting point of the resultantelectromagnetic repulsive force, means for stabilizing the engagement ofthe engaging parts, means for releasing the engagement thereof bydisplacing one of the contacting members having one of the engagingparts at the time the electromagnetic repulsive force exceeds apredetermined value, and means for restoring the engagement of theengaging parts after the opening of the two contacting points has beencompleted, whereby the contacting pressure between the contacting pointsof the contacting members is substantially increased when theelectromagnetic repulsive force is less than a predetermined value, andat least one of the contacting members abruptly opens the contacts whenthe electromagnetic repulsive force exceeds the predetermined value.

The nature, principle, and utility of the invention will be more clearlyapparent from the following detailed description with respect toexamples of preferred embodiment of the invention when read inconjunction with the accompanying drawings, in which like parts aredesignated by like reference numerals.

BRIEF DESCRIPTION OF DRAWINGS FIG. l is a sectional profile Iview of acircuit breaker according to the present invention shown in the closedstate;

FIG. 2 is a sectional prole view of the circuit breaker showing only theprinciple parts thereof which are manually brought into the open state;

FIG. 3 is a sectional profile view of the same circuit breaker showingonly the principal parts thereof which are brought automatically intothe open state;

FIG. 4 is a similar sectional profile view of the same circuit breakerwhich is brought into an initial automatic opening state by a currentlimiting mechanism;

FIG. 5 is also a sectional prole view of the same circuit breaker ywhichis brought into a maximum separating position by the automatic openingoperation of the current limiting mechanism;

FIG. 6 is an enlarged prole view showing the principal parts of thecurrent limiting mechanism;

FIG. 7 is an explanatory diagram for the operation of the currentlimiting mechanism; and

FIGS. 8, 9, and l() are enlarged views showing the principal parts onlyof other embodiments of the current limiting mechanism.

DETAILED DESCRIPTION Referring now to FIGS. l through 6, there isindicated a circuit breaker, each pole of which comprises a movablecontact member 1 having a contacting point 2 at one end thereof and astationary contact member 3 having a contacting point 4 likewise at oneend thereof and performing a switching action in cooperation with themovable contact member 1. Each pole of the circuit breaker alsocomprises a holder 5 mounted on an insulating shaft `6 commonly providedfor all poles of the circuit breaker, and the holder 5 is coupled to atrip lever 9 of the switching mechanism 101 through toggle links 7, 8.The movable contact member 1 is provided with an inverted V shapedcatching member t12 having a catching portion 10 and a cutout portion11, the catching portion 10 engaging Iwith a slit 14 of a trigger rod 13provided at an end of the holder 5.

Furthermore, the movable contact member 1 is, at a rotating axis 15provided thereon, rotatably connected to a link 16 which is alsorotatably mounted around a 3 shaft 17 on the holder 5. Between themovable contact member l1 and the holder 5, there is provided a tensionspring 18 which urges the link 116 to rotate counterclockwisely aroundthe shaft 17 until the movement of the link 16 is stopped by itsabutting against a stopper 19 provided on the holder so that theengagement between the catching portion and the trigger rod 13 isassured.

Since the movable contact member 1 andthe holder 5 are interlinked asdescribed above, these two members move in cooperation in the normalswitching operation of the circuit breaker.

When the circuit breaker is in the closed state as shown in FIG. 1, anelectric circuit is closed between one terminal 20 and the otherterminal 27 through a conductor 21, a flexible piece 22, the stationarycontact member 3, the movable contact member =1, another exible piece23, a conductor 24, a trip mechanism 36, and a conductor 26. As isapparent from FIG. 1, the circuit breaker is further provided with acasing 28, a cover 29, a contacting spring which urges the stationarycontact member 3 to rotate around a shaft 31 in the clockwise directionimparting a higher contact pressure against the movable contact member1, and a stopper pin 32 which limits the movement of the stationarycontact member after it is rotated through a predetermined angle at thetime the circuit breaker is brought into open state. Between a shaft 33which is linking the toggle links 7 and 8 and a handle 34 rotatablearound a pivotal point 25, tension springs 35 are provided.

When it is desired to open the circuit breaker by manual operation, thehandle 34 is thrown to the opening position maintaining a trip lever 9at an engaging position with a catch 37 of a tripping device 36, 'whichtrips the circuit breaker when an over current flows through thebreaker. At the time the handle 34 is thrown into the open position, theacting line of a tension of the springs 3S is shifted to the righthandside of a pivot pin 38, and the toggle links 7 and 8, thus being foldedback, in turn rotates the holder S around the axis 6, the rotation ofthe holder 5 opening the movable contact member 1 interlinked with theholder 5. FIG. 2 shows the thus opened state of the circuit breaker.

When the handle 34 is thrown into the closing position, the acting lineof the tension of the springs 35 is shifted back to the left side of thepivot pin 38, and under the action of this tension spring 35, the togglelinks 7 and 8 are brought into the extended positions, whereby thecontact members are closed as shown in FIG. 1 with a snap action.

When the tripping device 36 is operated through an over-current or ashort circuit current, the catch 37 is rotated clockwise around theshaft 39, and the trip lever 9 engaging with the catch 37 is rotatedcounterclockwise around the shaft 40, whereby the pivot pin 38 isshifted to the lefthand side of the acting line of the tension springs35. As a result, the toggle links 7 and 8 are folded back, rotating theholder S around the shaft 6, and the movable contact member 1interlinked with the holder 5 is brought into the opening state. Next,when the handle 34 is thrown into the closing position, the acting lineof the tension spring 35 is shifted to the left side of the pivot pin38, and under the action of the spring 35, the toggle links 7 and 8 arebrought to their straight states, whereby the contact members are closedas shown in FIG. 1 with a snap action. FIG. 3 shows the thus openedstate of the circuit breaker.

When it is desired to close again the circuit breaker after it has beenopened by the automatic tripping device 36, the handle 34 is moved fromthe above described tripped position rst to the opening position. Inthis way, a projection 42 of the catch 37 is pushed down by an end `41of the tripping lever 9, rotating the catch 37 in the counterclockwisedirection, and the catch 37 is again engaged ywith the tripping lever 9.Thus, the

circuit breaker is brought back from the state shown in FIG. 2 to thatof FIG. 1.

As is apparent from the above description, while the circuit breaker isoperated in manual closing and opening manner or in an automatic tripoperation, the movable contact member 1 and the holder 5 are operated 1nan interlinked manner, hence being operated similarly as in aconventional circuit breaker.

However, in the conventional construction of the tripping mechanism,there is a time delay of several m1111- seconds in theopening-and-closing operations from the instant the tripping device isoperated to the instant when the movable contact starts to operate, andwithin this delay time, the maximum value of the short circuitingcurrent passes through the circuit breaker. Although the passage of themaximum current through the circuit breaker does not create any problemif the short circuit current is of minor value, it would be preferableto open the contacts before the maximum current passes through thecircuit breaker so that the maximum current is thereby limited when theshort circuit current is of a considerably large rvalue.

The current limiting effect cannot be expected when a circuit breakerhaving no current limiting mechanism is employed. When a type ofconventional circuit breaker having a current limiting mechanism isemployed, the above described current limiting eiect may be obtained.However, such a type of conventional circuit breaker still has drawbackssuch as fusion seizure, sticking of the contact points, or over-heatingor burning of the contact points. According to the present invention, anovel type of the current limiting mechanism is provided whereby theabove described drawbacks of the conventional circuit breakers have beensubstantially eliminated.

The construction of the novel type of the current limiting mechanismwill now be described. Since the movable contact member 1 and thestationary contact member 3 are in their closing condition disposed inparallel as shown in FIG. 1, an electromagnetic repulsion force iscreated by the current owing therethrough. Although the repulsion forcecreated by the rated current for the circuit is moderate, the repulsionforce created at the time a short circuit current of high value flowsthrough the circuit breaker is of extraordinarily high magnitude becausethe repulsion force increases in proportion to the second power of theflowing current. The conventional construction of the current limitingmechanism has utilized this intensified electromagnetic repulsion forcedirectly for opening the contacts, and hence had the above describeddrawbacks such as fusion seizure.

As is apparent from FIG. 6, in the current limiting mechanism accordingto the present invention, the movable contact member 1 is provided witha catching portion 10 of the catching member 12 engaging with a slit 14on a triggering rod 13 provided at the tip of the holder 5 at a positionnearer to the contacting points than is the holder point of theelectromagnetic repulsion force. For this reason, when anelectromagnetic repulsion force is exerted, the movable contact member 1is subjected to a torque F1 acting in the counterclockwise directionaround the engaging point 102 between the catching portion 10 and theslit 14 of the triggering rod 13. On the other hand, since thestationary contact member 3 is freely rotatably mounted around the shaft31, which is positioned nearer to the contacting points than is theacting point of the electromagnetic force, the stationary contact member3 is subjected to a torque F3 in the clockwise direction caused by theelectromagnetic force around the shaft 31.

As described before, the stationary contact member 3 receives acontacting pressure in the closed state of the circuit breaker due tothe contacting spring 30, and this pressure constitutes a clockwisetorque F2 around the engaging point 102.

At a time when the electromagnetic repulsion force is Weak, and thetorque F1 cannot overcome the torque F2 due to the contacting pressure,the movable contact member 1 is maintained in the closed position.However, when the electromagnetic repulsion force becomes large, and thecounterclockwise torque lFl around the engaging point 102 overcomes thesum of the torques F2 and F3, the movable contact member 1 can berotated in the counterclockwise direction around the engaging point 102.

When such a condition occurs, the link 16 interlinking the movablecontact member '1 and the holder 5 is displaced around the shaft 17 atthe upper end thereof against the tension of the spring 18 as shown bychain lines in FIG. 6. The movable contact member 1 is shifted to thecontact side, as is most clearly apparent from FIG. 7, by a distance l,which in terms of the rotating angle 0 of the link 16 at this time, anangle a between the link 16 at the stationary condition and the verticalline, and the length l of the link 16 can be expressed as If thisshifted distance Al is less than the length S of the catching portion ofthe catching member 12 engaging with the slit 14 on the triggering rod13, the engagement of the movable contact member 1 at the engaging parts102 is not released. Thus, while the movable contact member 1 is notmoved or is not released from the engagement when it is moved slightly,the movable contact member 1 is subjected to a counterclockwise torqueF1 due to the electromagnetic repulsion force, and the stationarycontact member 3 is subjected to a clockwise torque.

As a result, the contacting pressure between the two contacting pointsis increased, and separation of the contacts or decrease of thecontacting pressure due to the increase in the current does not occur.When the current drops before the engagement is broken, the movablecontact member 1 is shifted back to its original stable state under theeffect of the spring 18, and the engagement at the point 102 is alsobrought back to the initial condition. Accordingly, over-heating orfusion seizure of the contact points which has frequently occurred inthe conventional circuit breakers is prevented.

When the electromagnetic repulsion force is further elevated, and thedisplacement Al of the movable contact member 1 becomes larger than thelength S of the catch porion 10, the engagement between the catchportion and the triggering rod 13 is broken. As a result, the movablecontact member 1 is rotated around the shaft 17 and also around theshaft 15 in cooperation with the link 16, whereby the separation of thecontact points due to the electromagnetic repulsion force is realized.'Ihis separation of the contact points is rapid because the separationis carried out through the swinging motion of the movable contact memberwhich has least inertia of rotation. It will also be apparent that theseparation speed of this contact is faster than in the conventionalconstruction wherein the separation is directly carried out by theelectromagnetic repulsive force because no decelerating effect due tothe contact pressure is created in the former case.

In this way, only the movable contact member 1 is separated before theseparation of the switching mechanism 101 occurs as shown in FIG. 4, andthe short circuit current is limited prior to the maximum value thereofis attained.

Until the condition as shown in FIG. 4 of the movable contact member 1is attained, the tripping operation due to the tripping device 36 of theswitching mechanism 101 is also started although it has a delay incomparison with the separating movement of the movable contact member 1.Accordingly, the separation of the contacting points further progresseswithout stopping in the state of FIG. 4 until the contacting points arein their maximum separaltion position `as shown in FIG. '5 so that `theinterruption of the short circuit current is assured.

After the state shown in FIG. 5 is attained, the movable contact member1 is sustained by a stopper shaft 43, and only the holder 5 continuesits upward movement. As a result, the triggering rod 13 is again raisedto the location of the catching portion 10, and, under the action of thetension spring 18, these are engaged together as they were in theinitial state. Thus, the opening operation of the circuit breaker iscompleted, and all of the components of the circuit breaker are in thesame positions as those when the breaker is automatically tripped onlyby the tripping device 36, which case is shown in FIG. 3, and theclosing operation thereafter can also be performed in the same manner.

As described above in detail, in the circuit breaker according to thepresent invention, the movable contact member 1 does not move out untila predetermined value of the electromagnetic repulsive force isattained, and the contacting pressure of the contacting points isthereby increased. When the electromagnetic repulsive force exceeds thepredetermined amount, the engagement between the triggering rod 13 andthe catching portion 10, both constituting the engaging parts 102described above, is broken, and the movable contact member 1 is thusfreed from the engagement to open the contacting points abruptly.

The circuit breaker according to the present invention thus permitsordinary manual switching operation and automatic switching operationsimilarly as in the case of an ordinary circuit breaker whenever theoverload current or a short circuit current passing therethrough is lessthan a predetermined value. More specifically, the circuit breaker isoperated manually or automatically by the tripping of the trippingdevice 36 but without operating the current limiting mechanism 100.However, when the overload current or the short circuit current exceedsthe above described preset value, the current limiting mechanismoperates and the above described fusion seizure or burning of thecontacting points is thereby prevented.

Although the present invention has been described with respect to apreferred embodiment thereof, it will be apparent to those skilled inthe art that various modifications or alternations may be made thereinWithout departing from the spirit and scope of the present invention.

For instance, while in the above described embodiment of the invention,the engaging parts 102 comprise the catching member 12 having a catchingportion 10 and a cutout portion 11 and provided on the part of themovable contact member 1 and the triggering rod 13 having a slit 14 andprovided on the holder 5 side, this may be modified as shown in FIG. 8so that the engaging parts 102 comprise a catching portion 44 and acutout portion 45 both provided on the holder 5 side and a triggeringrod 47 having a slit 46 and provided on the side of the movable contactmember 1.

Moreover, while the triggering rod 13 shown in FIGS. 1 through 6 andalso the tirggering rod 47 shown in FIG. 8 both having slits 14 and 46,respectively, have a semicircular cross section as apparent from thesefigures, these may be modified so that they have a cross section ofrectangular, of polygonal such as hexagonal, or of circularconfiguration.

Furthermore, in the above described embodiment, a link 16 has beenprovided between the shaft 15 on the movable contact member 1 andanother shaft 17 on the holder 5 for the purpose of shifting the movablecontact member 1 of the current limiting mechanism 100 to the contactpoint side by the electromagnetic repulsion force. However, this mayalso be replaced by another construction, as shown in FIG. 9, wherein anelongated hole 48 is obliquely provided on the movable contact member 1and a shaft 49 provided on the holder 5 is inserted in the hole 48.

Alternatively, as shown in FIG. l0, a shaft 50 may be provided on themovable contact member 1, and the shaft 50 may be inserted in a hole 51obliquely provided on the holder 5.

In the above described embodiment, the current limiting mechanism hasbeen provided only on the movable contact member side. However, thismechanism may be provided also on the stationary contact side, or two ofthe current limiting mechanisms may be provided respectively on themovable and stationary contact points may be doubled because of theprovision of the two current limiting mechanisms, the current limitingeffect in the circuit breaker is further improved.

We claim:

1. A circuit breaker comprising a movable contacting member and astationary contacting member both arranged so that an electromagneticrepulsive force is created therebetween by a current passing through thetwo members, a holder `connected with at least one of said two members,said at least one of the contacting members and said holder includingparts engageable at a position nearer to contacting points of said twocontacting members than the acting point of the resultantelectromagnetic repul* sive force, means for stabilizing the engagementof said engaging parts, means for releasing said engagement bydisplacing one of said contacting members having one of said engagingparts at the time the electromagnetic repulsive force exceeds apredetermined value, and means for restoring the engagement of saidengaging parts after the opening of the two contacting portions has beencompleted, whereby the contacting pressure between the contacting pointsof the contacting members is substantially increased when saidelectromagnetic repulsive force is less than a predetermined value, andat least one of said contacting members abruptly opens the contacts whensaid electromagnetic repulsive force exceeds the predetermined value.

2. A circuit breaker as dened in claim 1 wherein said holder isconnected with at least one of said contacting members through a linkboth ends of which are pivotally mounted on said holder and on said atleast one of the contacting members, respectively.

3. A circuit breaker as defined in claim 1 wherein said engageable partscomprise an inverted V shaped catching member provided on said at leastone of the contacting members and a triggering rod having an engagingslit provided on said holder.

4. A circuit breaker as del-ined in claim 1 wherein said holder isconnected with at least one of said contacting members through a linkboth ends of which are pivotally mounted on said holder and on said atleast one of the contacting members, respectively, and said means forstabilizing the engaging parts is a tension spring which, in cooperationwith said link, pulls said at least one of the contacting members to oneside so that the engagement of the engaging parts is thereby assured.

5. A circuit breaker as defined in claim 1 wherein said means forreleasing said engagement between said at least one of the contactingmembers and said holder comprises a link both ends of which arepivotally mounted on said holder and on said at least one of thecontacting members, respectively, whereby when the electromagneticrepulsive force exceeds a predetermined value, said at least one of thecontacting member having one of said engaging parts is displaced towardone direction and the engaging parts are thereby released.

6. A circuit breaker as defined in claim 1 wherein said engagementbetween said at least one of the contacting members and the holder isnot broken While the circuit breaker is tripped manually orautomatically by a separate tripping mechanism.

7. A circuit breaker as dened in claim 1 wherein said engaging portionscomprise a cutout portion provided on said holder and a triggering rodhaving a slit provided on said at least one of the contacting members.

8. A circuit breaker as dened in claim 1 wherein said holder and said atleast one of the contacting members are connected together by means ofan elongated slot and a pin combination instead of the link, and saidelongated slot is somewhat inclined against the longitudinal axes of theholder and said at least one of the contacting members.

References Cited UNITED STATES PATENTS 3,127,488 3/1964 Bodenschatz335-16 3,238,339 3/1966 Fehling 335--16 3,492,609 1/1970 Murai 335-163,500,266 3/1970 Torre 335-16 3,505,622 4/1970 Strobel 335--16 FOREIGNPATENTS 2,624,246 6/1968 Austria 335-16 HAROLD BROOME, Primary Examiner

